Gradient tint eyeglass lenses have been around for a long time. They are produced by dipping plastic lenses into a vat of hot tinting solution such that the upper portions of the lens spend more time in the dye than the lower portions. A state-of-the-art machine to do this was patented on Apr. 10, 1990, U.S. Pat. No. 4,915,986 by the inventors of the instant disclosure. That machine was called An Optical Lens Tinting Machine. Although that machine can and should be used with the invention of the present disclosure, it would be possible to use few other machines that produce gradient tints with the present invention, although the result would probably not be of the same quality.
The idea of the gradient tint is to permit the user to see the lower field of vision in full light while excluding some of the upper rays which would generally be considered as glare. In addition to reducing eye strain, gradient tint glasses can actually increase visibility by causing the iris to expand due to the upper shading, permitting more light to enter from the field of vision, which is often a roadway, a landscape, or even a book or computer.
Despite the benefits of the standard gradient tint, there is still a lot of glare that enters the eye in many situations, causing eye fatigue and unnecessary eye strain. This is particularly true during visual activities which are carried on much more in modern times than during the evolutionary development of the eye. For example, when watching television, reading a book, and especially when using a computer, it is only the light from a small cone of the observed field that is useful. The light from around this field of vision does not contribute to the proper viewing. For example, when using a computer, there are often bright fluorescent lights overhead or there may be daylight streaming in through a picture window. This light causes visually impairing refractions and reflections in the eye, and also reduces the aperture of the iris so that less light overall is admitted. This means that the computer will tend to look dim, while surrounding light areas are undesirably bright.
This is a principal well known to even amateur photographers, who know that the light readings on their light meters cannot be trusted when photographing a relatively dark subject with a bright background, or vice versa. Of course the eye cannot do this. It is miraculous that the eye can adjust as enormously as it does to varieties of light and dark, without expecting it to somehow diminish peripheral light from undesirable sources and amplify incoming light from the field of vision to accommodate the various visual activities of mankind. There is a need therefore, for a lens tinting system which will produce glasses which accomplish this function which is beyond the capability of the eye itself.